Flask ring



J. V. TURNER Aug. 14, 1934.

FLASK RING Filed Nov. 30, 1932 Patented Aug. 14, 1934- .uN Tso S1" reveal rarer OFICE 3 Claims.

This invention relates particularly to flask rin s of the type used in preparing investments or molds for casting dental articles.

In producing dental castings, it has been the practice to make a wax model of the part which it is desired to cast. A quantity of soft, plastic investmentcomposition is then placed in a cylindrical tubular metal flask ring, and the model is embedded or invested in this composition. After a short time, the composition hardens, and is capable ofwithstanding heat at high temperatures. Therithe whole investment including the flask. ring is heated tomelt out the Wax model which leaves .a mold cavity in the investment to receive metal to be cast. Molten metal is then forced into i the mold cavity, the investment being heated tov prevent too rapid chilling or cooling of the metal as it enters the cavity.

: Thereafter, the investment and the metal are allowed to 'cool, and when the metal has hardsued the investment is broken to remove the casting. a v The soft, plastic investment composition ex.- pands as it hardens or sets during the investment of the wax model, and as the flask ring used is a one-piece in'expansibleringfthcexpansion of the investment composition is not uniform in all directions, the only substantial expansion being in the direction of, the open ends of the cavity. This tends to cause distortion of the mold cavity. Also, when the investmentwiththe flask ring is heated andcooled during the casting operation, the expansion and contraction of the investment is not uniform in all directions which. tends to produce an inaccurately shaped casting. Furthermore, where the investment composition is leftin theflask ring during the castingoperation, it is necessary to heat the flask ring inaddition 0 to the composition, which leadsto diiiiculty in uniformly heating the flask'ring and the investment, and the heat conductivity and'coeflicients of expansion of the flask ring and theinvestment material-differ so that there is a tendency to dis- ,45, tortion of the mold cavity and the casting. Also,

ring of the general character'described embodying novel and improved features 'of construction whereby thefiask ring may expand in'directions at angles to itsaxis as the investment composition expands during'hardeningthereof to compensate for the expansion of theinvestment composition and ensure substantially uniform expansion thereof in all directions.

Another object is to provide a novel and improved flask ring of the character described embodying a plurality of separable sections whereby the flask ring can be easily and quickly removed from the block of investment composition after the latter has hardened and before heating thereof, so that during thecasting operation only the investment blockneed be heated.

-.A further object is to provide such a flask ring embodying novel and improved features of construction including a plurality of separable sections, and means for connecting them together so that they may relatively move during expansion of the investment composition while the latter is hardening, whereby the flask ring shall be expansible and can be easily and quickly removed from the investment block. 7

, Other objects are to provide a flask ring of the particular character described which shall be simple and inexpensive in construction and can be easily and quickly assembled and disassembled; and to obtain other advantages and results as will be brought out by the following description.

Referring to the accompanying drawing in which corresponding and like parts are designated throughout the several views by the same reference character,

Figure l is a perspective view of a flask. ring embodying my invention, showing the parts assembled to receive an investment.

Figure 2 is a composite perspective view of the parts of the flask ring disassembled.

Figure 3 is a transverse vertical sectional view through the flask ring. and an investment with a wax model therein.

Figure sis atop plan view of the structure shown in Figure 3. 7 Figure 5 is a transverse vertical view through the investment block with the flask ring removed and the waxmodel melted out, preparatory to the casting operation. 1 w

. Figure 6 is a fragmentary side elevation of a centrifugal casting apparatus with the investment block thereon at the beginning of the casting operation, and

Figure 7 is a view similar to Figure 1, showing a modification of the invention. Specifically describing the embodiment of "the invention illustrated in Figures 1 to 6 inclusive, the flask includes a ring, or elongated tubular or hollow body A to receive a soft, plastic investment composition in which a wax model is to be embedded and which will gradually harden vestment material.

after a period of time. This body Ais preferably expansible in directions at angles to its axis so as to permit corresponding expansion of said investment composition, and is shown as formed of a pair of complemental sections 1 and 2 which can be separated from each other or relatively moved apart so that the body may so expand, and also so that the hardened investment block can be easily removed from the body. These sections can be held together to form'the body A by any suitable means, such as a split ring 3 which embraces or surrounds the sections, said ring preferably being resilient or yieldable to permit relative movement of said sections in directions at angles to the axis of the body. Preferably, as shown each of said sections consists of a segment of an elongated cylindrical tubularor hollow body split on a plane parallel to and passing through the axis of said body, said sections cooperating when they are arranged with their longitudinal edges abutting each other, to form the body A. Also, preferably the split spring ring 3 is cylindrical or its walls are rectangular in cross section with the longer dimension longitudinal of the ring so as to snugly frictionally contact with the exterior walls of the body A.

When it is desired to; use the flask ring the two sections 1 and 2 are arranged with their longitudinal edges abutting as shown in Figure 1 and are slipped into the split ring 3, or the ring may be slipped over the sections from one end thereof. One edge of the split ring may be flared or rolled outwardly at 30 to guide the ends of the sections into the split ring or the split ring over the ends of the sections and serve as a finger-hold for sliding the rings on the sections. The cross sectional contour of the split ring 3 provides a snug uniform contact of the split ring with the flask sections over a large surface area which holds the sections 1 and 2 against relative twisting in the planes of their longitudinal edges and thereby maintains said longitudinal edges in accurate and tight contact throughout their lengths so that there is a minimum possibility of distortion of the investment. The body A may then be filled with a unitarymass of the soft, plastic investment composition B having a wax model C embedded therein, as usual, and as shown in Figure 3. As the composition B expands during hardening, the sections 1 and 2 may move relatively to each other in directions at angles to the axis of the body A so that the investment composition may expand substantially uniformly in all directions whereby there is a minimum possibility of distortion of the mold cavity formed around the wax model from non-uniform expansion of the investment composition; This relative yielding of the sections 1 and 2 thereby compensates the setting expansion of the in- After the investment block has hardened, thesplit ring 3 may he slipped from the body A," whereupon the two sections 1 and 2 maybe removed from the investment block. Thus the investment block can be easily and quickly separated from the flask ring without possibility of injury to the block.

Then the investment block may be heated to melt out thewax model. to form the mold cavity D without the necessityfor alsoheating the flask. ring, and all diiiiculty whichnflght arise during simultaneous heating of the investment block and the flask ring as usual, such as relative expansion and contraction of the block and flask ring and the waste of time in heating the flask ring, are eliminated.

' Also, during the casting operation onlythe invest ment block need be heated, and the block may expand uniformly in all directions so as to eliminate possibility of distortion of the mold cavity.

This is especially desirable where the casting operation is performed with my centrifugal casting machine described in my allowed copending application Serial No. 544,795, filed June 16, 1931, and which is fragmentarily illustrated in Figure 6. This machine includes a horizontal arm E rotatable by a vertical shaft F and having a yoke G pivoted at H on an axis parallel to that of the vertical shaft, said yoke having upstanding spaced arms I at one side of the pivot H on which a tray K is pivotally suspended on a horizontal axis L.

,The' investment block having the cavity D is mounted on the tray K with a piece of metal M of which the casting is to be formed, arranged on thetop of the block. The block and this metal are then heated in any suitable manner as by a blow torch N, after which the molten metal is forced into the mold cavity by centrifugal action upon rotation'of the shaft F. The heating operation may be quickly performed, and the block will quickly cool without impedance from a flask ring, and during heating and cooling the expansion and contraction will be substantially uniform in all directions so as to ensure against distortion of the mold cavity and the casting.

A modification of the flask ring is shown in Figure 7, where each of the complemental sections 4 and 5 of the tubular body is hingedly connected at one edge to one edge of the other, as indicated at 6, while the other edges have outwardly projecting longitudinal hooked flanges 7, which are separably connected by a channel shaped locking slide 8 having inturned flanges 9 which interlock with said hooked flanges '7, to hold said sections together to form the tubular body. Preferably the slide 8 is resilient, or extensible to yieldingly permit said sections to relaa longitudinal crimp 10 which permits lateral stretching or extension of the slide. In assembling this form of flask ring the sections 4 and 5 are swungtogether with their longitudinal edges abutting, and the locking slide 3 is slid endwise over the hooked flanges 7. To remove the investment block after it has hardened, the slide 8 is removed and the sections 4 and 5 are swung apart. The use and advantages of this form of flask ring are substantially the same as those of the flask ring shown in Figures 1 to 4 inclusive.

While I have shown and described two different forms of my invention'embodying various details of construction, it should be understood that this is primarily for the purpose of illustrating the principles of the invention and that the details of construction may be modified and changed without departing from the spirit of the invention. a

, Having thus described my invention, what I claim is: q

1. A flask ring for dental casting, comprising a pair of identical complemental sections each of which consists of a segment of a hollow tubular body split on an axial plane, and a split spring ring embracing said sections to hold them together with their longitudinal edges abutting to form a tubular body to receive a unitary mass of plastic investment .material, the walls of said split ring being rectangular in cross section Withthe larger dimension extending longie tudinally of the ring, whereby said sections may yield in directions at angles to the axis of the body to compensate setting expansion of said investment material.

2. A flask ring for dental casting comprising complemental sections each of which consists of a segment of a tubular body split on longitudinal planes, and a split spring ring embracing said sections to hold them together and form a tubular body to receive a unitary mass of plastic investment material, the walls of said split ring being rectangular in cross section with the larger dimension extending longitudinally of the ring, whereby said sections may yield in directions at angles to the axis of the body to compensate setting expansion of said investment material, one edge of said split ring being flared outwardly to facilitate application of said split ring to said tubular body and to serve as a finger hold.

3. A flask ring for dental casting comprising 

